Streptococcus agalactiae bacteria are a common cause of neonatal sepsis and meningitis. Universal screening of pregnant women for carriage and intrapartum antibiotic prophylaxis has significantly reduced the disease prevalence in children up to 7 days of age. However, it is to be remembered that group B streptococcal infection can also affect older children, even if their mothers have tested negative for Streptococcus agalactiae during pregnancy or underwent complete perinatal antibiotic prophylaxis. This paper presents a clinical case of a 3-month-old boy treated for sepsis and Streptococcus agalactiae meningitis. The baby was born on time, with normal body weight. The infection occurred despite full maternal ampicillin perinatal therapy in the mother.